The spelling of the word "doest part" may seem unusual, but it follows Early Modern English conventions. In IPA phonetic transcription, it would be /dʌst pɑrt/. "Doest" is the second person singular present tense of the verb "do" in Early Modern English, whereas "part" means "to depart". So the phrase "doest part" means "you depart" in Early Modern English. Although this spelling is no longer used in contemporary English, it serves as a reminder of the evolution of language over time.
The phrase "doest part" is an archaic form of the verb "do" in the present tense, second person singular. It has its roots in Old English, where "doest" was used as the second person singular present form of the verb "don", meaning "to do" or "to perform". Over time, the construction "doest part" emerged, which means "you do" or "you perform". However, it is worth mentioning that this phrase is no longer in common usage in contemporary English.